摘要:

Excess viscosities, excess volumes, and excess free energies of activation for flow of the binary mixtures containing propionic acid with aniline,o-toluidine,o-anisidine, ando-chloroaniline were determined at five different temperatures from density and viscosity measurements. Based on the Regular Solutions Theory, the empirical parameter θ was calculated; this parameter is related to the viscosity, and also denotes the extent of the non-ideality of the system. The results obtained suggest the existence of acid–base interactions, as well as the formation of 1:2 complexes for the three first mixtures, and 2:1 complexes foro-chloro-aniline + propionic acid. The extent of the specific interaction decreases with an increase in the strength of the base, and increases with an increase in the dipole moments. The equatioinis proposed for predicting the mole volume of the mixtures,V, at any composition, Xi, as a function of the mole volumes of the pure components,Vi.Keywords: binary mixture, excess properties, predicting mole volumes, propionic acid.

ISSN:0008-4042    

DOI:10.1139/v91-056

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

3,3-Dialkyl-3H-pyrazole-4,5-dicarboxylic acid dimethyl esters (4), obtained by cycloaddition of R1R2C=N+=N−(R1 = R2 = CH3; R1 = CH3, R2 = CH2CH3) to CH3O2CC≡CCO2CH3, rearrange thermally by 1,5-sigmatropic alkyl shifts to both N and C. The latter rearrangement is followed by two successive 1,5-sigmatropic shifts of a methoxycarbonyl group. Final products of the threefold rearrangement were shown to be 4,5-dialkyl-1H-pyrazole-1,3-dicarboxylic acid dimethyl esters (6), rather than the isomeric 3,4-dialkyl-1H-pyrazole-1,5-dicarboxylic acid dimethyl esters (7), by means of single crystal X-ray diffraction. Those products therefore result from alkyl migration to C-4 of4, followed by sequential migration of the methoxycarbonyl group, initially at C-4, to C-3 and then to N-2 of4. In the initial alkyl migration step, ethyl migrates in preference to methyl, and in subsequent migration steps the methoxycarbonyl group migrates faster than the ethyl or methyl group. Crystals of 4-ethyl-5-methyl-1H-pyrazole-1,3-dicarboxylic acid dimethyl ester (6b) are monoclinic, of space groupP21/n, witha = 7.907(1) Å,b = 11.087(2) Å,c = 13.199(3) Å,V = 1124.9(4) Å3,Dc = 1.34 g cm−3,Dm = 1.33 g cm−3forZ = 4, andR1 = 0.0772 (R2 = 0.0626) for 1474 reflections (R1 = 0.0428,R2 = 0.0422 for 903 reflections withI > 3σ(I)). The structure of6ais similar.Keywords: 3,3-dialkyl-3H-pyrazoles, 1,5-sigmatropic rearrangements of; 4,5-dialkyl-1H-pyrazoles, crystal and molecular structures; 1,5-sigmatropic rearrangements of pyrazoles, sense of.

ISSN:0008-4042    

DOI:10.1139/v91-057

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Abietic acid (1a) has been converted into the pregnane analogue steroid10via a sequence of transformations involving as key step the acetylene-cation cyclization of9.Keywords: abietic acid, pregnane steroids, acetylene-cation cyclization

ISSN:0008-4042    

DOI:10.1139/v91-058

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

2-S-Methyl-5,5-dimethylimidazolin-4-one can be crystallized as Δ1or Δ2tautomers, depending on the solvent polarity. The structure, solved on crystals obtained from benzene, showed it to be the Δ1tautomer in theanticonfiguration. Δ1-2-S-Methyl-5,5-dimethylimidazolin-4-one is monoclinic, space groupP21/c,witha = 8.347(1),b = 10.121(1),c = 9.996(3) Å, β = 107.20(2)°,R = 0.037 for 1395 independent reflections withI > lσ(I). The quantum mechanical (MNDO, PM3, and AMI) calculations indicate that among the four conformers theanti-Δ1tautomer has both the lowest dipole moment and the lowest enthalpy of formation. The ultraviolet spectrum of the title compound has been recorded in solvents with different dielectric constants. The infrared spectra of the Δ1and Δ2solid samples are discussed relative to thev(NH) andv(CO) absorptions and in comparison with those recorded in carbon tetrachloride and in chloroform solution. Its acid–base behaviour has been studied by determining the pKain aqueous solutions and the results are compared with those obtained for some related hydantoins.Keywords: 2-S-methyl-5,5-dimethylimidazolin-4-one, tautomerism, hydantoin derivatives, crystal structure.

ISSN:0008-4042    

DOI:10.1139/v91-059

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Single crystals of gold(III) tris(fluorosulfate) are obtained by recrystallization from bis(fluorosulfuryl) peroxide, S2O6F2, under O2pressure. The crystals of [Au(SO3F)3]2are monoclinic,a = 9.700(4),b = 9.222(2),c = 10.810(4)Å, β = 94.43(3)°,Z = 2, space groupP21/a. The structure was solved by heavy atom methods and was refined by full-matrix least-squares procedures,R(F) = 0.038 andRw(F) = 0.050 for 1491 reflections withI ≥ 3σ(I). The structure consists of centrosymmetric [Au(SO3F)3]2dimers containing two bidentate, symmetrically bridging and four monodentate, terminal SO3F ligands. The Au(III) ions have square-planar coordination geometry with bridging Au—O = 2.020(7) and 2.016(6) Å, and terminal Au—O = 1.959(7) and 1.956(9) Å. The dimeric [Au(SO3F)3]2units are linked in the solid state by weak Au—O interactions (2.757(8) and 2.960(7) Å), resulting in a distorted octahedral coordination geometry about each gold atom.Keywords: gold(III) tris(fluorosulfate), crystal structure.

ISSN:0008-4042    

DOI:10.1139/v91-060

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The reaction of NH4TcO4with PPh3in DMF solution in the presence of HCl producesmer-Tciii(PPh3)2Cl3(DMF)•2PPh3(1). When the reaction is done in acidic DMA, the yellow product isolated was identified as NH2(CH3)2+DMAH+[TcCl6]2−•PPh3O (2). The dimethylammonium cation was produced from the reaction of the solvent (DMA) with aqueous HCl. The reaction of NH4TcO4with PPh3in acidic acetone solution produces yellow (PPh3H)2[TcCl6] (≈15% yield) and some orange crystals (≈65% yield) identified by X-ray diffraction as [Ph3P-C(CH3)2-CH2-CO-CH3]+[Tc(PPh3)Cl5]−. The cation was produced from the reaction of acetone used as solvent with HCl and PPh3. The crystals of1are monoclinic withP21/mspace group,a = 11.393(4),b = 24.993(11),c = 12.398(4) Å, β = 106.98(3)°,Z = 2. The structure was refined toR = 0.072 andwR = 0.058. The Tc—O bond distance is 2.115(12) Å while the Tc—P bond lengths are 2.496(5) and 2.499(5) Å and the Tc—Cl are 2.399(5) and 2.342(3) Å. The C atoms of the DMF ligand are disordered. The crystals of2are triclinic,space group witha = 8.627(5),b = 13.308(7),c = 14.401(9) Å, α = 97.62(5), β = 91.31(5), γ = 106.42(5)°, andZ = 2. The structure was refined toR = 0.060 andwR = 0.076. The proton on DMAH+is hydrogen bonded to the oxygen of PPh3O with a distanceKeywords: technetium, DMF, triphenylphosphine, dimethylacetam

ISSN:0008-4042    

DOI:10.1139/v91-061

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

For the title systems, single crystal X-ray data indicate the presence of totally asymmetric structures. These features are reflected in the multiplicity of resonances in the solid phase13C NMR spectra. Some of the13C chemical shift trends are analyzed in terms of torsional angle influences. In solution, resonance assignments have been made with the aid of 2D methods. Stereochemical inferences are drawn from NOESY spectra and1H–1H couplings. Low temperature solution experiments indicate that conformational interconversions in both the free ligand and the NaNCS complex are rapid on the NMR timescale down to 163 K.Keywords: crown ethers, NMR, stereochemistry.

ISSN:0008-4042    

DOI:10.1139/v91-062

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

δ-Valerolactone (3), on treatment with tris(methylthio)methyllithium (7) followed by weakly acidic aqueous work-up, gave a tautomeric mixture of 1, 1-bis(methylthio)-6-hydroxy-2-hexanone (8a) and tetrahydro-2-bis(methylthio)methyl-2-pyranol (8b). Under analogous conditions3reacted with tris(phenylthio)methyllithium (10) to form tetrahydro-3-(phenylthiocarbonyl)-2-pyranone (11). With 2-(methylthio)-1,3-dithian-2-yllithium (16) it gave a tautomeric mixture of 2-(5-hydroxy-1-oxopentyl)-2-(methylthio)-1,3-dithiane (17a) and 2-(tetrahydro-2-hydroxy-2-pyranyl)-2-(methylthio)-1,3-dithiane (17b). Treatment of17with methanol in the presence of acidic ion-exchange resin gave a mixture of 2-(5,6-dihydro-3-(methylthio)-2(4H)-pyranyl)-1,3-dithiane (20), 2-(tetrahydro-2-methoxy-2-pyranyl)-1,3-dithiane (21), and 2-(tetrahydro-2-methoxy-4-(methylthio)-2-pyranyl)-1,3-dithiane (22). Similar treatment of20gave a mixture of20,21, and22. Compound21was synthesized independently by similar treatment of 2-(tetrahydro-2-hydroxy-2-pyranyl)-1,3-dithiane (23). The origins of the anomalous products are discussed briefly. It is concluded that because of these anomalies the preparation of tetrahydro-2-hydroxypyran-2-carboxylic acid acetals and related glycosides via trithio-orthoformate derivatives can encounter difficulties, although dithioacetals may serve this purpose.Keywords: 1,3-dithianes, α-hydroxy acids,δ-lactones, trithio-orthoformates.

ISSN:0008-4042    

DOI:10.1139/v91-063

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The boron difluoride complexes of 2-acetylcyclohexanone, 2-acetylcyclopentanone, and acetylacetone (abbreviated as ACHBF2, ACPBF2, and AABF2) were irradiated in the presence of benzene to give the 1:1 adducts as the primary photoadducts; for certain BF2complexes, toluene, chlorobenzene, benzonitrile, and methyl benzoate were also used as substrates. The 1,5-diketone photoadducts were assumed to form by a [2+2] photocycloaddition followed by cyclobutane opening and hydrolysis to give 1,2 adducts. They undergo a variety of secondary thermal reactions, probably acid catalyzed, to give enol ethers, enol acetates, acetophenones, and ketonylacetophenones. The efficiency of these secondary reactions determines the final products. Photoaddition with a monosubstituted benzene preferentially occurs at the 3,4 bond without regioselectivity. Under oxygen, ACHBF2photolytically reacts with benzene to give a secondary oxidation product of a 10-membered cyclic alkylphe-none, which is proven by X-ray crystallographic analysis to have the benzene ring and carbonyl group in orthogonal orientation. It is shown that the singlet excited state ACHBF2initiates the photoaddition, probably through the formation of the benzene exciplex, which could be detected by its emission. While the Stern–Volmer rates are small, the quantum yield of photoaddition products is as high as 0.12–0.19 under limiting conditions.Keywords: [2+2] photocycloaddition, non-planar alkanophenone, macrocyclic alkanophenone, boron difluoride complexes, photoaddition to benzenes.

ISSN:0008-4042    

DOI:10.1139/v91-064

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Novel and reliable methods for the synthesis of the polymers [Cu(4-Xpz)2]x(where X = H, Cl, Br, and Me; pz = pyrazolate) are presented. The X = Cl compound was obtained as green and brown forms. Single crystals of the polymers with X = Me and X = Cl (green form) suitable for X-ray analysis have been obtained. [Cu(4-Mepz)2]xand [Cu(4-Clpz)2]xare isomorphous, crystallizing with four formula units per unit-cell in the orthorhombic space groupIbam,a = 9.7436(6), 9.155(4),b = 12.6106(8), 12.968(6), andc = 7.7482(6), 7.717(5) Å, respectively, for the 4-Me and 4-Cl derivatives. The structures were refined by full-matrix least-squares procedures toR = 0.027 and 0.041 for 430 and 246 reflections withI ≥ 3σ(I), respectively. Magnetic susceptibility studies over the temperature range 2 to 300 K have revealed that all the polymers exhibit very strong antiferromagnetic exchange between copper(II) centres in the extended linear chains. Discontinuities displayed in the susceptibility versus temperature plots suggest the presence of phase transitions at ~133 and ~108 K in the X = Cl (green form) and X = Br materials, respectively. The four compounds, X = H, Br, Me, and Cl (green form) also exhibit thermochromism over the 77 to 176 K region. The magnetic data have been analyzed employing an isotropic Heisenberg model for antiferromagnetic exchange in extended chain polymers. Values of the exchange coupling constant,J, for the room temperature forms of these materials are determined as −81, −105, −96, −104, and −88 cm−1for 4-X = H, Br, Me, Cl (green form), and Cl (brown form), respectively. The magnitude of the exchange coupling is discussed in relation to structural parameters for the X = H, Me, and Cl (green form) compounds.Keywords: copper(II) 4-substituted pyrazolate polymers, crystal structures, magnetic exchange.

ISSN:0008-4042    

DOI:10.1139/v91-065

出版商:NRC Research Press    

年代:1991

数据来源: NRC